The present invention relates to an improved bearing and to an abrading apparatus using the bearing. More particularly, the present invention relates to an improved cylinder machine using an improved spherical bearing for the polishing and fining of ophthalmic lenses.
Generally speaking, ophthalmic lenses are initially generated or molded to the approximate curve desired and then finished by fining and polishing on a suitable lapping apparatus. Usually the lens surface is lapped by a cylindrical finisher which moves a lapping tool held in engagement with the lens surface in an irregular path to first fine and then polish the lens. One cylindrical finisher is disclosed in U.S. Pat. No. 3,732,647, May 15, 1973 to Stith.
The Stith apparatus has a vertical rod, the upper end of which supports a lap carrier. The middle of the shaft is pivotally supported by a gimbal assembly and the lower end of the shaft is driven in an orbital motion. The gimbal limits rotation of the shaft about its own longitudinal axis. This is important because the lapping tool at the upper end of the shaft must be maintained in accurate rotational alignment with the surface of the lens to be ground in order to grind compound or cylindrical lenses without axis error. In one aspect, the present invention is in the nature of an improvement of the Stith apparatus which can be achieved by use of a spherical bearing of the present invention instead of the gimbal of the Stith apparatus. The present invention provides a means for correcting machine induced axis error. In addition, the present invention provides an improved support means which can be more easily sealed from the environment, which has less vibration, which requires less maintenance, and which has fewer moving parts than does a gimbal apparatus. These and other advantages of the present invention will become apparent from the accompanying drawings and the following disclosure.